Wednesday, December 31, 2014

What does Percent Not Converging Mean in SWMM5?

In SWMM 5 there is a Routing time step summary which tells the modeler the minimum time step during the simulation based on the CFL condition, the average time step, maximum time step, the percent of time spent in steady state, the average iterations per step and the percent not converging.  The percent not converging means the percent of the time the link flows and node depths did not converge within the maximum number of trials per time step (Figure 1).

  Routing Time Step Summary
  Minimum Time Step           :     0.52 sec  
  Average Time Step           :     8.76 sec
  Maximum Time Step           :    10.00 sec
  Percent in Steady State     :     0.00
  Average Iterations per Step :     2.14
  Percent Not Converging      :     1.69

Figure 1.  Maximum number of trials per time step
The Percent Non Converging is the percent of time at least ONE link did not converge within the maximum number of trials per time step.  The Percent Non Converging is the Total Number of Non Convergent Steps divided by the total number of steps during the simulation.

Here is how the converging and non converging is determined in the dynamic wave solution.

The program keeps iterating until the Steps taken during this time step equals the Number of Maximum Trials. During each time step the link flows and the node depths are calculated.  If the Steps are greater than 1 and all nodes depths are converged (the difference between successive iterations is less than the Head tolerance) then the iteration process stops.  If even one node does not converge the Non Converge Count increases by one.   The links that can be bypassed during the next step are also estimated at each iteration. If a link can be bypassed the dynamic wave calculations are not performed and the program runs faster (Figure 2).
Figure 2.  Link Bypass is based on the Upstream and Downstream Nodes

    // --- keep iterating until convergence 
    while ( Steps < MaxTrials )
        // --- execute a routing step & check for nodal convergence
   converged = findNodeDepths(tStep);
        if ( Steps > 1 )
            if ( converged ) break;

            // --- check if link calculations can be skipped in next step
    if ( !converged ) NonConvergeCount++;

    //  --- identify any capacity-limited conduits

    return Steps;

Tuesday, December 30, 2014

How to Make a Trapezoidal Inflow Time Series in InfoSWMM

You can make a Trapezoidal shaped Time Series in InfoSWMM by using the following steps:
  1. .       Use the Inflow Icon at a Node in the Attribute Browser
  2. .       Use either an Inflow Time series with date/time/value or
  3. .       A baseline flow value with a pattern
  4. .       The time series comprise a Date that matches your simulation time period
  5. .       A hour:minute:second Time value in the Time Series Table
  6. .       A flow unit with the units used in the General Tab of Run Manager
  7. .       This time series is entered in the Attribute Browser under Time Series in the Operation Tab
How to Make An Inflow Time Series at a Node in InfoSWMM

Sunday, December 28, 2014

The EPA SWMM 5 code and the various versions of Visual Studio

The EPA SWMM 5 code and the various versions of Visual Studio. If you have multiple versions of Visual Studio on your computer you might have toolset issues.  Visual Studio 2010 and 2012 are for Windows 7, Visual Studio 2013 is for Windows 8

Visual Studio 2012 uses the v11 toolset

Visual Studio 2013 uses the v12 toolset

Visual Studio Configuration Properties

Thursday, December 25, 2014

How to Make Scatter Graphs in InfoSWMM and H2OMap SWMM

How to Make Scatter Graphs in InfoSWMM and H2OMap SWMM

Scatter graphs of velocity on the X axis and depth on the Y axis are important to help understand the reason for flow/depth relationships in flow surveys.  You can make a scatter graph in InfoSWMM by plotting the link flow and the by clicking on the Report button.  A right mouse click will bring up the Data Scatter Plot option. The column on the left of the selected columns will be the X Axis column of data. The column on the right will be the Y Axis column of data.  The default is depth followed by velocity. The order variables can be changed by using the Format Icon (bullet 1) followed by the Scatter Plot selection of velocity/depth (see Figure 1 for an example).  Figure 2 shows how to make a Log/Log Scatter Graph in InfoSWMM using the Properties Icon.

Figure 1.  The Basic Velocity vs Depth Scatter Graph in InfoSWMM

Figure 2.  The Log/Log Options for a Scatter Graph.

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